Thermoplastic elastomer composition and process for producing the same

ABSTRACT

A thermoplastic elastomer composition characterized in that the composition comprises a resin component and at least two kinds of rubber components, wherein at least one kind of the rubber components makes a continuous phase and/or a network-like phase, and the remaining at least one kind of the rubber components makes an isolated phase; and a process for producing the same.

TECHNICAL FIELD

The present invention relates to a thermoplastic elastomer compositionand a process for producing the same. More specifically, the presentinvention relates to a thermoplastic elastomer composition havingsuperior scratch resistance, and a process for producing the same.Further, the present invention also relates to a thermoplastic elastomercomposition having superior abrasion resistance and superiormechanicalproperties (particularly, elongation at break) as well as superiorscratch resistance.

BACKGROUND ART

A thermoplastic elastomer has not been required to have scratchresistance, because a molded article obtained by molding thethermoplastic elastomer is used after coating thereon with a coatingagent, and the coated layer has scratch resistance. In recent years,there are less and less articles having such a coated layer, therefore,scratch resistance of material is highly regarded, and, in some cases,their abrasion resistance is also highly regarded in addition to thescratch resistance. And, their levels required are becoming higher andhigher. Taking the present condition into consideration, it is difficultto say that a conventional process for producing a thermoplasticelastomer is always satisfactory.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a thermoplasticelastomer composition having superior scratch resistance and a processfor producing the same.

Another object of the present invention is to provide a thermoplasticelastomer composition having superior abrasion resistance and superiormechanical properties (particularly, elongation at break) as well assuperior scratch resistance.

That is, the present invention provides a thermoplastic elastomercomposition comprising a resin component and at least two kinds ofrubber components, wherein at least one kind of the rubber componentsmakes a continuous phase and/or a network-like phase, and the remainingat least one kind of the rubber components makes an isolated phase.

Further, the present invention provides a process for producing theabove-defined thermoplastic elastomer composition, which comprisesfeeding a resin component and a rubber component making an isolatedphase in a kneading machine, melt-kneading them or heat-treating themdynamically, and thereafter feeding a rubber component making acontinuous phase and/or a network like-phase therein.

Still further, the present invention provides a thermoplastic elastomercomposition having the above-defined structure, which contains:

-   -   (A) a copolymer of an aromatic vinyl compound and ethylene        and/or an α-olefin,    -   (B) a rubber selected from the group consisting of (b1) a        hydrogenated aromatic vinyl compound-conjugated diene compound        copolymer rubber, and (b2) a copolymer rubber of ethylene and an        α-olefin having not less than 4 carbon atoms, and    -   (C) an olefin based resin.

Still further, the present invention provides a thermoplastic elastomercomposition having the above-defined structure, which is obtained byheat-treating dynamically in the presence of a cross-linking agent or inthe presence of a cross-linking agent and a cross-linking co-agent:

-   -   (A) an ethylene and/or α-olefin-aromatic vinyl compound        copolymer,    -   (B) (b3) an ethylene-α-olefin based copolymer rubber, and    -   (C) an olefin based resin.

The present invention is explained in detail as follows.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration defining a shape of an isolated phase and asize thereof.

FIG. 2 is an illustration showing an isolated phase and a continuousphase.

FIG. 3 is an illustration showing a partially continuous phase and anentirely continuous phase.

FIG. 4 is an illustration showing an incompletely continuous phase and acompletely continuous phase.

FIG. 5 is an illustration a network-like phase and a continuous phase.

FIG. 6 is a transmission microscopic photograph obtained in Example 1.

FIG. 7 is a transmission microscopic photograph obtained in ComparativeExample 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The thermoplastic elastomer composition in accordance with the presentinvention has a phase structure, which comprises a resin component andat least two kinds of rubber components, wherein at least one kind ofthe rubber components makes a continuous phase and/or a network-likephase, and the remaining at least one kind of the rubber componentsmakes an isolated phase.

Examples of the rubber component used for the composition of the presentinvention are a rubber and a thermoplastic elastomer. As the rubber, anisoprene based rubber, a butadiene based rubber, a chloroprene rubber, anitrile rubber, a butyl rubber, an acrylic rubber, an olefin basedrubber, an epichlorohydrine rubber, a polysulfide rubber, a siliconerubber, a fluororubber and an urethane rubber are exemplified, and apreferable rubber component is an isoprene based rubber, a butadienebased rubber or an olefin based rubber. Examples of the isoprene basedrubber are a natural rubber and an isoprene rubber, examples of thebutadiene based rubber are a butadiene rubber, a styrene-butadienerubber and 1,2-polybutadiene, and examples of the olefin based rubberare an ethylene-α-olefin based copolymer rubber and an ethylene and/orα-olefin-aromatic vinyl compound based copolymer rubber. As theethylene-α-olefin based copolymer rubber, an ethylene-α-olefin copolymerrubber and an ethylene-α-olefin-conjugated diene copolymer rubber areexemplified.

Examples of the above-mentioned thermoplastic elastomer are a styrenebased thermoplastic elastomer, an olefin based thermoplastic elastomer,an urethane based thermoplastic elastomer, an ester based thermoplasticelastomer, an amide based thermoplastic elastomer, a vinyl chloridebased thermoplastic elastomer, trans1,4-polyisprene and an ionomer, anda preferable thermoplastic elastomer is a styrene based thermoplasticelastomer, an olefin based thermoplastic elastomer, trans1,4-polyispreneor an ionomer. Examples of the styrene based thermoplastic elastomer area styrene-butadiene-styrene block copolymer (SBS), astyrene-isoprene-styrene block copolymer (SIS), a hydrogenatedstyrene-butadiene-styrene block copolymer (SEBS), a hydrogenatedstyrene-isoprene-styrene block copolymer (SEPS) and a hydrogenatedstyrene-butadiene rubber (HSBR), and an example of the olefin basedthermoplastic elastomer is a reactor TPO.

As the rubber component, an oil-extended rubber, which contains an oil,may be used.

An example of the oil is a mineral oil such as paraffin, naphthene andaromatic mineral oils. Of these, paraffin mineral oils are preferred.

In the present invention, a combination of the rubber components isselected, wherein at least one kind of the rubber components makes acontinuous phase and/or a network-like phase, and the remaining at leastone kind of the rubber components makes an isolated phase. In selectingsuch a combination, for example, it is preferred that viscosity of therubber component making an isolated phase is larger than that of therubber component making a continuous phase and/or a network-like phase.When viscosity of the rubber component making an isolated phase isalmost the same as that of the rubber component making a continuousphase and/or a network-like phase, it may happen that only an isolatedphase or only a continuous phase is made. Further, in selecting such acombination, it is preferred that at least one kind of rubber componentsis a diene rubber component having a double bond in its structure, andthe remaining at least one kind of rubber components is a non-dienerubber component having no double bond therein.

Furthermore, it is preferred to select a combination of a copolymer ofan aromatic vinyl compound and ethylene and/or an α-olefin as acontinuous phase-making rubber (A) with (b1) a hydrogenated aromaticvinyl compound-conjugated diene compound copolymer, (b2) anethylene-α-olefin (having 4 or more carbon atoms) copolymer rubber or(b3) an ethylene-α-olefin (having 3 or more carbon atoms) basedcopolymer rubber as an isolated phase-making rubber(B).

When selecting the above-mentioned combination of a diene rubbercomponent with a non-diene rubber component, preferred examples of thediene rubber component are natural rubber, isoprene rubber, butadienerubber, styrene-butadiene rubber, ethylene-α-olefin-conjugated dienecopolymer rubber, styrene-butadiene-styrene copolymer andstyrene-isoprene-styrene copolymer. And preferred examples of thenon-diene rubber component are a hydrogenated styrene-butadiene-styrenecopolymer, a hydrogenated styrene-isoprene-styrene copolymer, ahydrogenated styrene-butadiene rubber, an ethylene and/orα-olefin-aromatic vinyl compound copolymer, an ethylene-α-olefincopolymer and a reactor TPO. When a combination of the diene rubber withthe non-diene rubber is selected, an isolated phase and a continuousphase can be easily made by heat-treating dynamically in the presence ofa cross-linking agent.

An isolated phase means a phase wherein the same component (the rubbercomponent) does not continue but disperses individually, or means aphase wherein the same component (the rubber component) is dispersed ina continuous phase like a particle form, in an observation of a crosssection of the thermoplastic elastomer composition. The isolated phasehas a shape such as a circle, an oval, a needle and an amorphous. And,particles having a different shape may be present. A size of theisolated phase is preferably not more than 500 μm in average, and morepreferably not more than 50 μm in average. Each size of the shapes otherthan circles is defined by a diameter of a circumscribed circle. Withrespect to a circle or a shape close to a circle, it is preferably notmore than 10 μm. When the isolated phase is too large, the surface maybecome sandy, and as a result, appearance may deteriorate.

A continuous phase means a phase wherein the same component (the rubbercomponent) continues and disperses partially or entirely, or continuesand disperses completely or incompletely, in an observation of a crosssection of the thermoplastic elastomer composition. The entirelycontinuous phase means that the continuous phase is made in the entireregion of the thermoplastic elastomer composition, and the partiallycontinuous phase means that the continuous phase is made in a partialregion of the thermoplastic elastomer composition. The completelycontinuous phase means a continuous phase having no isolated phasetherein, and the incompletely continuous phase means a continuous phasepartially making an isolated phase.

A network-like phase means a phase wherein the isolated phases are boundwith one another to continue and disperse entirely or partially, orcompletely or incompletely, in an observation of a cross section of thethermoplastic elastomer composition. The entirely continuous phase meansthat the continuous phase is made in the entire region of thethermoplastic elastomer composition, and the partially continuous phasemeans that the continuous phase is made in a partial region of thethermoplastic elastomer composition. The completely continuous phasemeans a continuous phase having no isolated phase therein, and theincompletely continuous phase means a continuous phase partially makingan isolated phase.

It is particularly recommendable to use a combination of a copolymer ofethylene and/or an α-olefin and an aromatic vinyl compound as the rubbercomponent (A) making the continuous phase and rubber selected from thegroup consisting of (b1) a hydrogenated aromatic vinylcompound-conjugated diene compound copolymer and (b2) ethylene-α-olefin(having 4 or more carbon atoms) copolymer rubber as the rubber (B)making the isolated phase, and to use an olefin based resin as theresin, because there can be provided a thermoplastic elastomercomposition having superior abrasion resistance and superior mechanicalproperties (particularly elongation at break) as well as superiorscratch resistance. It is also recommendable to use a rubber combinationof an ethylene and/or α-olefin-aromatic vinyl compound copolymer (A) andan isolated phase-making ethylene-α-olefin (having 3 or more carbonatoms) based copolymer rubber (b3), and to subject such a combinationand the olefin based resin (C) to dynamic heat-treatment in the presenceof a cross-linking agent or in the presence of a cross-linking agent anda cross-linking co-agent, thereby obtaining a thermoplastic elastomercomposition having the above-mentioned structure, because there can beobtained a thermoplastic elastomer composition having physicalproperties similar to the above.

The ethylene and/or α-olefin-aromatic vinyl compound copolymer (A) is arandom copolymer. Examples of the α-olefin constituting the copolymerare propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene,1-octene and 1-decene.Among them, preferable is propylene, 1-butene,1-hexene or 1-octene. Examples of the aromatic vinyl compound are analkyl styrene such as p-methylstyrene, m-methylstyrene, o-methylstyrene,p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, 2,4-dimethylstyrene,2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene,3-methyl-5-ethylstyrene, p-tert-butylstyrene and p-sec-butylstyrene;styrene; an alkenylbenzene such as 2-phenyl-1-propylene and2-phenyl-1-butene; a bisalkenylbenzene such as divinylbenzene; and avinylnaphthalene such as 1-vinylnaphthalene. Among these alkenylaromatic compounds, styrene, p-methylstyrene, m-methylstyrene,o-methylstyrene, p-tert-butylstyrene, 2-phenyl-1-propylene,divinylbenzene or 1-vinylnaphthalene is preferable, and styrene isparticularly preferable, from a viewpoint of easy synthesis andcopolymerizability (easy production of a monomer, and easycopolymerization with ethylene and/or an α-olefin).

A content of the aromatic vinyl compound is preferably from 5 to 50% byweight, and more preferably from 10 to 35% by weight. Incidentally, thesum of the aromatic vinyl compound, ethylene and the α-olefin is 100% byweight. When the content of the aromatic vinyl compound is less than 5%by weight, the obtained composition may deteriorate in its elasticityand transparency. On the other hand, when the content exceeds 50% byweight, its elasticity may deteriorate. As the copolymer of ethyleneand/or α-olefin and the aromatic vinyl compound, a random copolymer ispreferred, and an ethylene-aromatic vinyl compound copolymer isparticularly preferred from a viewpoint of flexibility and elasticrecovery.

The above-mentioned copolymer of ethylene and/or α-olefin and thearomatic vinyl compound can be produced according to a process describedin U.S. Pat. No. 6,187,889 or EP laid open No. 1002808.

The hydrogenated aromatic vinyl compound-conjugated diene compound blockcopolymer as the rubber component (B) includes a (I)-(II) blockcopolymer, a (I)-(II)-(III) block copolymer and a (I)-(II)-(I) blockcopolymer, wherein (I) is an aromatic vinyl compound polymer block, (II)is a conjugated diene polymer block or an aromatic vinylcompound-conjugated diene random copolymer block, and (III) is anaromatic vinyl compound-conjugated diene copolymer tapering block, inwhich the aromatic vinyl compound component in the copolymer increaseslittle by little toward a definite direction of the polymer chain.

Examples of the aromatic vinyl compound are styrene, an α-methylstyrene,p-methylstyrene, vinylxylene and vinylnaphthalene, and styrene ispreferable. Examples of the conjugated diene compound are butadiene,isoprene, 2,3-dimethyl-1,3-butadiene and2-neopentyl-1,3-butadiene, andfrom an industrial point of view, butadiene or isoprene is preferable,and butadiene is the most preferable. A content of the aromatic vinylcompound is preferably 10 to 60% by weight, and more preferably 10 to40% by weight. When said content is less than 10% by weight or more than60% by weight, mechanical properties may decrease.

Although a degree of hydrogenation is not particularly limited, it isgenerally 70% or more, preferably 80% or more, and more preferably 90%or more of a polymerized conjugated diene.

Further, a preferable example of the α-olefin in the copolymer rubber(b2) of ethylene and the α-olefin having 4 or more carbon atoms is anα-olefin having 4 to 12 carbon atoms such as 1-butene, 1-pentene,1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene. Among them,1-butene, 1-hexene or 1-octene is preferable. A content of the α-olefinis preferably 10 to 50% by weight, and more preferably 20 to 40% byweight.

Specific examples of the copolymer (b2) of ethylene and the α-olefinhaving 4 or more carbon atoms are an ethylene-1-butene copolymer rubber,an ethylene-1-pentene copolymer rubber, an ethylene-1-hexene copolymerrubber, an ethylene-1-octene copolymer rubber and an ethylene-1-decenecopolymer rubber.

Further, examples of the ethylene-α-olefin based copolymer rubber (b3),which is used for obtaining a thermoplastic elastomer composition by adynamic heat-treatment in the presence of a cross-linking agent or inthe presence of a cross-linking agent and a cross-linking co-agent, area copolymer rubber of ethylene and an α-olefin having 3 or more carbonatoms and a copolymer of ethylene, said α-olefin and a polyene. Examplesof the α-olefin in the copolymer rubber are propylene, 1-butene,1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene. Amongthem, preferable is propylene, 1-butene, 1-hexene or 1-octene. Examplesof the polyene are a linear chain non-conjugated diene such as1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene,6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene; a cyclicnon-conjugated diene such as cyclohexadiene, dicyclopentadiene,methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene,5-methylene-2-norbornene, 5-isopropylidene-2-norbornene and6-chloromethyl-5-isopropenyl-2-norbornene; and a triene such as2,3-diisopropylidene-5-norbornene,2-ethylidene-3-isopropylidene-5-norbornene,2-propenyl-2,2-norbornadiene, 1,3,7-octatriene and 1,4,9-decatriene.Among them, a cyclic non-conjugated diene is preferable,and5-ethylidene-2-norbornene or dicyclopentadiene is particularlypreferable. A content of the diene is preferably 5 to 40 and morepreferably 10 to 20 in terms of an iodine value.

Specific examples of the ethylene-α-olefin based copolymer rubber (b3)are those of the copolymer rubber of ethylene and an α-olefin having 3or more carbon atoms exemplified above and an ethylene-propylenecopolymer rubber, an ethylene-1-butene copolymer rubber, anethylene-1-hexene copolymer rubber, anethylene-propylene-5-ethylidene-2-norbornene copolymer rubber and anethylene-propylene-dicyclopentadiene copolymer rubber.

As the ethylene-α-olefin based copolymer rubber (b3), preferred arethose having Mooney viscosity at 100° C. (ML₁₊₄ 100° C.) of preferablyfrom 5 to 150, and more preferably from 20 to 100. When the Mooneyviscosity is less than 5, mechanical strength may markedly deteriorate.On the other hand, when the Mooney viscosity exceeds 150, the moldedarticle may deteriorate in its appearance. Incidentally, when oilextended rubber is used as the ethylene-α-olefin based copolymer rubber,a value of Mooney viscosity of such an oil extended rubber is based onthat of the ethylene-α-olefin based copolymer rubber containing anextender oil.

Examples of oils used for the oil-extended rubber are paraffin,naphthene and aromatic mineral oils. Of these, paraffin mineral oils arepreferred.

The resin component makes a phase in the space excluding the rubbercomponent, which phase is an isolated phase and/or a continuous phase.

The resin component used in the present invention is a thermoplasticresin. Examples of the thermoplastic resin are olefin based resins,styrene based resins, vinyl chloride based resins, acrylic based resinsand carbonate based resins. Of these, olefin based resins or styrenebased resins are preferred. A mixture of the olefin resin and thestyrene resin may be used. Examples of the styrene resin arepolystyrenes and high impact polystyrenes. The most preferred is theolefin based resin.

Examples of the olefin based resin (C) are an ethylene based resin, apropylene based resin and a butene based resin, and these resins may beused alone or in a mixture thereof. Examples of said ethylene basedresin are a high density polyethylene, a low density polyethylene, alinear low density polyethylene and an ethylene copolymer containingethylene as a main monomer. Examples of said ethylene copolymercontaining ethylene as a main monomer are an ethylene-vinyl acetatecopolymer, an ethylene-methyl methacrylate copolymer and a copolymer ofethylene and an α-olefin having 3 to 12 carbon atoms. Examples of saidpropylene based resin are a propylene homopolymer and a copolymercontaining propylene as a main monomer. Examples of said copolymercontaining propylene as a main monomer are a copolymer of propylene andan α-olefin having 2 or 4 to 12 carbon atoms and a polypropylene graftedby styrene or a functional group. As the α-olefin in thepropylene-α-olefin copolymer, ethylene is preferable, and examples of apropylene-ethylene copolymer are a random copolymer and a blockcopolymer. Examples of said butene resin are 1-butene homopolymer and acopolymer of 1-butene and other monomer(s).

As the olefin based resin, a propylene based resin is preferable from aviewpoint of heat resistance and industrialization.

The olefin based resin has a melt flow rate (JIS-K-7210, 230C, 21.18 N),hereinafter referred to as MFR, of preferably from 0.1 to 150 g/10 min,and more preferably from 1 to 100 g/10 min. When MFR is less than 0.1g/10 min, moldability may deteriorate, and on the other hand, when MFRexceeds 100 g/10 min, mechanical properties may markedly deteriorate.

More specifically, examples of the propylene based resin are a propylenehomopolymer (C1), a propylene-ethylene random copolymer (C2) and apropylene-ethylene block copolymer (C3). A combination containing atleast two of (C1), (C2) and (C3) may be used.

With respect to the propylene homopolymer (C1), those having highcrystallinity are preferred, when the stiffness is desired to be high.

With respect to the propylene-ethylene random copolymer (C2), thosehaving a low ethylene content or having high crystallinity arepreferred, when the stiffness is desired to be high. On the contrary,those having a high ethylene content or having low crystallinity arepreferred, when the stiffness is desired to be low. Which is selectedcan be determined depending upon the purposes.

The propylene-ethylene block copolymer (C3) comprises a first segmentand a second segment, wherein the first segment is a homopolypropyleneportion obtained in homopolymerizing propylene, and the second segmentis a propylene-ethylene random copolymer portion. It is permitted touse, as the first segment, a propylene-ethylene random copolymer havinga different ethylene content from that of the second segment. When thestiffness is desired to be high, those having a low content of thesecond segment, namely the propylene-ethylene random copolymer portion,or those having a low ethylene content in the propylene-ethylene randomcopolymer portion are preferred. Which is selected can be determineddepending upon the purposes.

With respect to the content of respective components in thethermoplastic elastomer composition in accordance with the presentinvention, a content of (A) is preferably from 10 to 80% by weight, acontent of (B) is preferably from 10 to 80% by weight, and a content of(C) is preferably from 60 to 10% by weight, provided that(A)+(B)+(C)=100 parts by weight. When (A) is less than 10% by weight,the scratch resistance and the abrasion resistance may deteriorate, andon the other hand, when (A) exceeds 80% by weight, the mechanicalproperties may deteriorate. When (B) is less than 10% by weight, themechanical properties may deteriorate, and on the other hand, when (B)exceeds 80% by weight, the scratch resistance and the abrasionresistance may deteriorate. When (C) is less than 10% by weight, theflowability may deteriorate to result in poor moldability, and on theother hand, when (C) exceeds 60% by weight, the scratch resistance andthe abrasion resistance may deteriorate.

In the present invention, in addition to the above-mentioned rubbercomponent and resin component, inorganic fillers such as talc, calciumcarbonate and calcined kaolin; organic fillers such as organic fibers,wood powder and cellulose powder; lubricants such as fatty acid amidesand silicones; antioxidants such as a phenol antioxidan, a sulfurantioxidan, a phosphorus antioxidan, a lactone antioxidan and a vitaminantioxidant; weather stabilizers; ultraviolet absorbers such as abenztriazol ultraviolet absorber, a triazine ultraviolet absorber, ananilide ultraviolet absorber and a benzophenone ultraviolet absorber;heat stabilizers; light stabilizers such as a hindered amine lightstabilizer and a benzoate light stabilizer; anti-static agents;nucleating agents and pigments may be used.

In order to improve the abrasion resistance moreover, it is preferred tocontain the inorganic filler, and it is more preferred to contain theinorganic filler and the lubricant. For obtaining a thermoplasticelastomer composition having flexibility, calcium carbonate ispreferred.

For obtaining the thermoplastic elastomer composition in accordance withthe present invention, a continuous type or batch type kneading machinemay be used to perform melt-kneading. As the continuous type kneadingmachine, a single screw extruder and a twin screw extruder areexemplified. As the batch type kneading machine, a kneader and Banburymixer are exemplified. Depending upon the shape of the resin componentand the rubber component, the batch type and the continuous type may beused at the same time. If necessary, a dynamic heat-treatment using across-linking agent or a combination of a cross-linking agent and across-linking co-agent may be carried out.

As a method for feeding the resin component and the rubber component,even if the resin, the isolated phase-making rubber and the continuousphase and/or network-like phase-making rubber are fed at the same timein the kneading machine and kneaded therein, at least one rubbercomponent can make the continuous phase and/or network-like phase, andthe remaining at least one rubber component can make the isolated phase.However, it is preferred to feed and knead the resin component and theisolated phase-making rubber into the kneading machine, melt-dispersethem and thereafter feed the continuous phase and/or network-likephase-making rubber therein. When a dynamic heat-treatment is applied,it is permitted to feed the resin, the isolated phase-making rubber andthe continuous phase and/or network-like phase-making rubber in thekneading machine, or to feed the resin and the isolated phase-makingrubber in the kneading machine, and after completing the dynamicheat-treatment feed the continuous phase and/or network-likephase-making rubber into the kneading machine. However, when the dienerubber is used for both the isolated phase-making rubber and thecontinuous phase and/or network-like phase-making rubber, or thenon-diene rubber is used for both the isolated phase-making rubber andthe continuous phase and/or network-like phase-making rubber, it isnecessary to feed the resin and the isolated phase-making rubber intothe kneading machine, and after completing the dynamic heat-treatmentfeed the continuous phase and/or network-like phase-making rubber intothe kneading machine.

As the cross-linking agent used for the dynamic heat-treatment, sulfur,organic peroxides and phenol resins are exemplified. Organic peroxidesare preferred. Specific examples of the organic peroxides used are2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexyn,1,3-bis(t-butylperoxyisopropyl)benzene,1,1-di(t-butylperoxy-3,5,5-trimethylcyclohexane),2,5-dimethyl-2,5-di(peroxybenzoyl)hexyn and dicumyl peroxide.

As the cross-linking co-agent, compounds having two or more double bondsin the molecular structure are preferred. Specific examples thereof areN,N′-m-phenylene bismaleimide, toluylene bismaleimide, p-quinonedioxime, nitrosobenzene, diphenylguanidine, trimethylolpropanetrimethacrylate and divinylbenzene.

An amount of the cross-linking agent in the dynamic heat-treatmentcarried out in the presence of the cross-linking agent can be determinedappropriately within a range of preferably from 0.01 to 10 parts byweight, which range is not limitative.

An amount of the cross-linking co-agent can be also determinedappropriately within a range of preferably from 0.1 to 10 parts byweight, which range is not limitative.

The thermoplastic elastomer composition in accordance with the presentinvention can be used in extrusion molding, injection molding, pressmolding, blow molding and powder molding.

There can be applied for various uses, and examples thereof are partsfor automobiles, railroads, air-planes and ships, electric appliances,building parts for construction, stationery and sundry goods, whereinscratch resistance or both the scratch resistance and abrasionresistance are required.

Further, the thermoplastic elastomer composition in accordance with thepresent invention can be used in multi-layer molding and a sheet. Apreferred example of a multi-layered article is an article molded bymeans of two-layer molding, wherein a core portion comprises the olefinresin and a skin portion comprises the thermoplastic elastomercomposition in accordance with the present invention. When the skinportion is desired to have a sense of softness, the thermoplasticelastomer composition has a hardness (shore A) of preferably not morethan 99, and more preferably from 90 to 60. As the olefin resin for thecore portion, propylene resins, ethylene resins and olefin thermoplasticelastomers are exemplified.

For obtaining the above-mentioned article molded by means of two-layermolding, for example, co-extrusion with use of an extruder, coinjectionmolding and insert molding can be applied.

As preferred embodiments of the multi-layered article, car interiorparts are exemplified. Specific examples thereof are instrumentalpanels, doors, arm rests, grab rails, shift knobs, instrumental grips,side brake knobs, console boxes, glass runs and weather strips.

The present invention is explained in more detail with reference to thefollowing Examples.

EXAMPLE

[I] Raw Materials

(A) Continuous Phase-making Rubber

(a-1) Ethylene-styrene Copolymer

The ethylene-styrene copolymer (ESC) was produced by continuouslycopolymerizing ethylene and styrene using a 100 liter SUS polymerizationreactor equipped with a stirring blade. That is, from the bottom of thepolymerization reactor, hexane as a polymerization solvent, ethylene andstyrene were continuously supplied at the rate of 84.7 kg/hr, 2.8 kg/hrand 4.15 kg/hr, respectively. On the other hand, from the top of thepolymerization reactor, the resulting polymerization liquid wascontinuously taken out so as to keep the polymerization liquid in thepolymerization reactor to 100 liters. As a catalyst,isopropylidene(cyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titanium dichloride,N,N-dimethylaniliniumtetraxis(pentafluorophenyl)borate andtriisobutylaluminum were continuously supplied in the polymerizationreactor from the bottom thereof at the rate of 0.348 g/hr, 1.081 g/hrand 6.912 g/hr, respectively. The copolymerization reaction was carriedout at 50° C. while circulating cooled water in a jacket mounted on theoutside of the polymerization reactor. A little ethanol was added to thepolymerization liquid taken out of the polymerization reactor toterminate the polymerization reaction, followed by removal of monomerand water washing. Thereafter, the solvent was removed by means of steamin a large amount of water, thereby isolating the copolymer, which wasdried overnight under reduced pressure. According to the operationmentioned above, the ethylene-styrene copolymerization was carried outat the rate of 2 kg/hr. The copolymer was found to have intrinsicviscosity [η] of 2.31 dl/g, measured at 135° C. using an Ubbelohdeviscometer and tetralin as a solvent. Using a differential thermalanalyzer (DSC 220 manufactured by Seiko Instruments Inc.), a fusioncurve was obtained using the programmed temperature rate of 10° C./min,and as a result, a melting point and a glass transition point were foundto be 44° C. and −20° C., respectively.

A styrene content measured by means of ¹³C-NMR (JNM-EX 270 manufacturedby JEOL Ltd.), measurement solvent: o-dichlorobenzene, measurementtemperature: 135° C.) was found to be 16 mol %, and a ratio of a peakarea appearing on 34.0˜36.0 ppm to that appearing on 36.0˜38.0 ppm wasfound to be 0.019.

(B) Isolated Phase-making Rubber

(b-1) Hydrogenated Styrene-butadiene-styrene Copolymer b-1-1 ;Commercial name: TUFTEC H1042 (hydrogenated styrene-butadiene-styrenecopolymer), manufactured by Asahi Chemical Industry Co., Ltd.

(b-2) Ethylene-α-olefin Copolymer Rubber

(b-2-1) Oil Extended Ethylene-propylene-non-conjugated Diene CopolymerRubber

[Mooney viscosity (ML₁₊₄100° C.)=79, non-conjugated diene=ENB, amountoil extended=40 parts by weight based on 100 parts by weight of rubber]

(b-2-2) Ethylene-1-butene Copolymer Rubber

MFR (190° C., 21.18 N)=0.6 g/10 min, butene content=17% by weight

(b-2-3) Ethylene-propylene Copolymer Rubber

MFR (190° C., 21.18 N)=0.7 g/10 min, propylene content=27% by weight

(C) Olefin Resin

(c-1) Propylene-ethylene Block Copolymer

MFR (JIS-K-7210, 230° C., 21.18 N)=65 g/10 min, NOBLENE AX568,manufactured by Sumitomo Chemical Co., Ltd.

[II] Measurement Method

The composition obtained was molded with a press molding machine at 200°C., thereby obtaining a 150 mm×150 mm flat plate having a thickness of 2mm, which was then subjected to measurements desired.

(1) Phase observation: an ultra-thin piece sliced with anultra-microtome was dyed with RuO₂ to obtain a specimen, which wasobserved with a transmission electron microscope (6000 magnifications).

(2) Scratch resistance test: using a surface property tester (SHINTOSCIENTFIC Co., Ltd.), a surface of a plate obtained by press molding wasscratched with a scratching needle, which was loaded with a 300 g weightand moved at a definite speed, and the resulting scratch was visuallyobserved to obtain an evaluation,

-   -   ◯; good (scratch is not remarkable), and    -   X; bad (scratch is remarkable).

(3) Abrasion resistance test: cloth (shirting No. 3) and a plate weremounted to a color fastness rubbing tester, a load of 500 g was appliedthereto and an abrasion surface through mirror rubbing of 200 times withthe cloth was visually observed to obtain an evaluation,

-   -   ◯; good (abrasion is not remarkable), and    -   X; bad (abrasion is remarkable).

(4) Tension test: a plate obtained by press molding using a JIS No.3dumbbell was punched to prepare a specimen, which was pulled at the rateof 200 mm/min with a tension tester, thereby finding break strength andelongation at break (according to JIS-K-6251).

Example 1 and Comparative Example 1

To the blend as shown in Table 1, 0.1 part by weight of a cross-linkingco-agent, trimethylolpropane trimethacrylate, and 0.128 parts by weightof a cross-linking agent, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyn wereadded in two equal divisions, followed by dynamic heat-treatment with alaboplastomill. The obtained composition was molded, and the moldedarticle was measured. The results are as shown in Table 1. TABLE 1Example 1 Comparative Example 1 a-1 15 parts by weight b-1-1 15 parts byweight b-2-1 30 parts by weight 60 parts by weight c-1 40 parts byweight 40 parts by weight Scratch resistance ◯ X Phase observation Acontinuous phase Only an isolated and an isolated phase was observed.phase comprising (FIG. 7) rubber were observed. (FIG. 6)

Example 2 and Comparative Example 2

The blends shown in Table 2 were melt-kneaded with a laboplastomill,respectively. Each of the obtained compositions was molded, and themolded article was measured. The results are as shown in Table 2. TABLE2 Comparative Example 2 Example 2 Blending (parts by weight) a-1 30b-1-1 30 60 c-1 40 40 Evaluation result Break strength(MPa) 5.1 3.0Elongation at break(%) 120 280 Scratch resistance ◯ X Abrasionresistance ◯ X

Examples 3 and 4 and Comparative Example 3

The blends shown in Table 3 were melt-kneaded with a laboplastomill,respectively. Each of the obtained compositions was molded, and themolded article was measured. The results are as shown in Table 3. TABLE3 Example Comparative 3 4 Example 3 Blending (parts by weight) a-1 30 30b-2-2 30 60 b-2-3 30 c-1 40 40 40 Evaluation result Break strength(MPa)6.2 3.2 4.3 Elongation at break(%) 130 70 170 Scratch resistance ◯ ◯ XAbrasion resistance ◯ ◯ X

Example 5

To the blend as shown in Table 4, 0.1 part by weight of a cross-linkingco-agent, trimethylolpropane trimethacrylate, and 0.128 parts by weightof a cross-linking agent, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyn wereadded in two equal divisions, followed by dynamic heat-treatment with alaboplastomill. The obtained composition was molded, and the moldedarticle was measured. The results are as shown in Table 4. Physicalproperties of the composition obtained in the foregoing ComparativeExample 1 are also shown therein. TABLE 4 Comparative Example 5 Example1 Blending (parts by weight) a-1 30 b-2-1 30 60 c-1 40 40 Evaluationresult Break strength(MPa) 5.3 3.9 Elongation at break(%) 410 350Scratch resistance ◯ X Abrasion resistance ◯ XIndustrial Applicability

As mentioned above, the present invention can provide a thermoplasticelastomer composition having superior scratch resistance, and a processfor producing the same.

1. A thermoplastic elastomer composition comprising a resin componentand at least two kinds of rubber components, wherein at least one kindof the rubber components makes a continuous phase and/or a network-likephase, and the remaining at least one kind of the rubber componentsmakes an isolated phase.
 2. The thermoplastic elastomer compositionaccording to claim 1, wherein said at least one kind of the rubbercomponents is a rubber having a double bond, and said remaining at leastone kind of the rubber components is a rubber component having no doublebond.
 3. The thermoplastic elastomer composition according to claim 1,wherein the resin component is an olefin based resin or a styrene basedresin.
 4. The thermoplastic elastomer composition according to claim 1,wherein the rubber component making a continuous phase and/or anetwork-like phase is an ethylene-aromatic vinyl compound copolymerand/or an α-olefin-aromatic vinyl compound copolymer (A), the rubbercomponent making an isolated phase is a rubber (B) selected from thegroup consisting of (b1) a hydrogenated aromatic vinylcompound-conjugated diene compound copolymer rubber, and (b2) acopolymer rubber of ethylene and an α-olefin having not less than 4carbon atoms, and the resin component is an olefin based resin (C). 5.The thermoplastic elastomer composition according to claim 4, whereinthe aromatic vinyl compound in (A) and (b1) is styrene, and theconjugated diene compound in (b1) is butadiene.
 6. The thermoplasticelastomer composition according to claim 4, wherein (C) is a propylenebased resin.
 7. The thermoplastic elastomer composition according toclaim 4, wherein a content of (A) is 10 to 80% by weight, a content of(B) is 10 to 80% by weight, and a content of (C) is 60 to 10% by weight,based on 100% by weight of a sum of (A), (B) and (C).
 8. Thethermoplastic elastomer composition according to claim 1, which isobtained by heat-treating dynamically the following components (A), (b3)and (C) in the presence of a cross-linking agent or in the presence of across-linking agent and a cross-linking co-agent: (A): an ethyleneand/or α-olefin-aromatic vinyl compound copolymer, (b3): a copolymerrubber of ethylene and α-olefin having not less than 3 carbon atoms, and(C) an olefin based resin.
 9. The thermoplastic elastomer compositionaccording to claim 8, wherein the cross-linking agent is an organicperoxide, and the cross-linking co-agent is a compound having at leasttwo double bonds in its molecular structure.
 10. The thermoplasticelastomer composition according to claim 8, wherein the aromatic vinylcompound in (A) is styrene.
 11. The thermoplastic elastomer compositionaccording to claim 8, wherein (b3) is anethylene-α-olefin-non-conjugated diene copolymer rubber.
 12. Thethermoplastic elastomer composition according to claim 8, wherein (C) isa propylene based resin.
 13. The thermoplastic elastomer compositionaccording to claim 4, wherein a content of (A) is 10 to 80% by weight, acontent of (B) is 10 to 80% by weight, and a content of (C) is 60 to 10%by weight, based on 100% by weight of a sum of (A), (B) and (C).
 14. Asheet comprising a thermoplastic elastomer composition according toclaim
 4. 15. A multi-layer molded article, whose core portion comprisesan olefin resin and skin portion comprises a thermoplastic elastomercomposition according to claim
 4. 16. A sheet comprising a thermoplasticelastomer composition according to claim
 8. 17. A multi-layer moldedarticle, whose core portion comprises an olefin resin and skin portioncomprises a thermoplastic elastomer composition according to claim 8.18. A process for producing a thermoplastic elastomer compositionaccording to claim 1, which comprises feeding a resin component and arubber component making an isolated phase in a kneading machine,melt-kneading them or heat-treating them dynamically, and thereafterfeeding a rubber component making a continuous phase and/or a networklike-phase therein.